Third point doesn't mean that this object can prevent XSS or Ajax JavaScript Hijacking problems but if You write secure applications You should believe in its features to prevent malicious code.For example, if You reload this object each interaction during a server response You'll be more secure during Array or Object convertion using code evaluation but please read Ajax security problems to know more.

You can find this object here while You can read documentation page (thanks to Natural Doc) using this link.